Multiple security enhancements for image steganography

Abstract

As the requirement for securing data has increased, novel approaches like reversible data hiding have been developed. Reversible data hiding is one among the many methods to securely store message into a cover media like image. Drawbacks of this method were overcome with the help of novel approaches like Separable reversible data hiding. Separable reversible data hiding is an improvised method in which there are two key players : the content owner and the data hider. The former encrypts the original image with an encryption key while the later exploits the spatial correlation of the natural image to create an additional space to accommodate data. At the receiver side, receiver having the data-hiding key, can extract the data but not the original image. At the same time, the receiver with the encryption key, can extract the image but not the data. If he has both the data-hiding and the encryption keys, he can extract the data and the original image content. The efficacy of this method can be enhanced if the keys too can be secured. This can be done using an efficient key-exchange algorithm like the Diffie-Hellman Key Exchange Algorithm. Also use of multiple encryption methods would make the system compatible with different applications. The system, in its working environment, would come across various actors with different privileges. In such a situation, having an authentication system would ensure that the data is received at the right hands. An authentication system and attack prevention measures, integrated along with the current version makes Separable Reversible data hiding a formidable method for data security.

Full text

Multiple Security Enhancements for
Image Steganography
Megha Mohan
Department of Computer Science and Engineering
Mar Baselios College of Engineering and Technology
Trivandrum, India
Email: meghamohan1992@gmail.com
Abstract—As the requirement for securing data has increased,
novel approaches like reversible data hiding have been
developed. Reversible data hiding is one among the many
methods to securely store message into a cover media like image.
Drawbacks of this method were overcome with the help of novel
approaches like Separable reversible data hiding.
Separable reversible data hiding is an improvised method in
which there are two key players : the content owner and the data
hider. The former encrypts the original image with an encryption
key while the later exploits the spatial correlation of the natural
image to create an additional space to accommodate data. At the
receiver side, receiver having the data-hiding key, can extract the
data but not the original image. At the same time, the receiver
with the encryption key, can extract the image but not the data. If
he has both the data-hiding and the e ncryption keys, he ca n
extract the data and the original image content.
The efficacy of this method can be enhanced if the keys too
can be secured. This can be done using an efficient key-exchange
algorithm like the Diffie-Hellman Key Exchange Algorithm. Also
use of multiple encryption methods would make the system
compatible with different applications. The system, in its working
environment, would come across various actors with different
privileges. In such a situation, having an authentication system
would ensure that the data is received at the right hands. An
authentication system and attack prevention measures,
integrated along with the current version makes Separable
Reversible data hiding a formidable method for data security.
Keywords—Reversible data hiding, Separable reversible data
hiding, Symmetric keys, AES, DES, Diffie Hellman key exchange.
I. INTRODUCTION
The growth of data and its security are major research
areas under consideration in current scenario of
steganography. There is a tremendous growth in the size of
data being processed and also it is a tedious process for
handling them. There are various methods used for securing
the data which is transmitted through the shared medium. One
such method is hiding the data into a cover media. The cover
media may be of type text, image, audio or video. As the
requirement of securing data (image and text) has increased,
novel approaches like reversible data hiding have been
developed.
Reversible Data Hiding system is a non-separable method that
is, the user must have both the image encryption key as well as
Anitha Sandeep
Department of Computer Science and Engineering
Mar Baselios College of Engineering and Technology
Trivandrum, India
Email: anitha.sandeep@gmail.com
the data embedding keys to get the hidden data. This affects
the flexibility of the system [3]. In order to overcome
limitations of this system, a new system was proposed which
was both separable and reversible in nature.
Separable reversible data hiding is one in which there are two
key players, the content owner and the data hider [1]. The
former encrypts the original image with an encryption key
while the later exploits the spatial correlation of the natural
image to create an additional space to accommodate data. At
the receiver side, receiver having the data-hiding key, can
extract the data but not the original image. At the same time,
the receiver with the encryption key, can extract the image but
not the data. If he has both the data-hiding and the encryption
keys, he can extract the data and the original image [1]
content.
Separable reversible data hiding technique can be integrated
along with certain efficient encryption algorithms like DES
and AES for encrypting both the image as well as the data.
This further improves the strength of the system and makes
the system immune to eavesdroppings. Also use of multiple
encryption methods would make the system compatible with
different applications.
The efficacy of this method can be further enhanced if the
keys too can be secured. This can be done using a powerful
key-exchange algorithm like the Diffie-Hellman Key
Exchange Algorithm. The system, in its working environment,
would come across various actors with different privileges. In
such a situation, having an authentication system would ensure
that the data is received at the right hands. An authentication
system and attack prevention measures, integrated along with
the current version makes Separable Reversible data hiding a
formidable method for data security.
In the following sections, section
II gives a brief about
the existing Separable Reversible
Data Hiding Technique
is given. Followed by is section III in which the proposed
system i.e. the enhanced method of Separable Reversible Data
Hiding along with Secure Key Exchange is explained, then
section IV, dealing with Experimental results of the proposed
system. Finally is the conclusion which is disc ussed under
section V.
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II. EXISTING SYSTEMS
A. Reversible data hiding
Reversible data hiding (Fig 1) is one among the many methods
used to securely exchange message by implanting a message
into some cover media provided and then sending it to the
destination. These methods are reversible in nature as the
original cover image can be recovered as such, after the
hidden message has been retrieved. The cover image used may
be an image that cannot tolerate any deformation, like
sensitive images - military images or remote sensing images or
medical images. At the destination, after extracting the hidden
message, the original cover image can be retrieved back
perfectly and hence this method is a reversible process[3].
Recently various types of reversible data hiding methods are
advised.
Advantages of this technique is that, the security of the
messege as well as the cover image is ensured. So another
improved method Separable reversible data hiding was
considered [5]. Though various novel changes have been made
in the reversible data hiding technique they have certain
drawbacks. One such drawback is non-separability i.e. both
keys are required to retrieve the embedded data as well as the
original cover image with desired resolution. Hence the
system was modified to overcome some of its drawbacks and
a novel system known as Separable Reversible Data Hiding
was introduced.
Fig. 1. Reversible data hiding [3]
B. Separable Reversible data hiding
The term separable means ’something that is possible to
separate’ [1]. In this concept, the separation of actions:
decryption of the actual cover image and retrieval of secret
(data which was embedded) takes place independent of each
other. The separation of actions is done based on keys
available (Fig 2).
At the destination, there are three different cases chanced
during extraction : (a) cover image only, (b) payload only, (c)
both payload and cover image [1].
Advantages of using this method is that, data and image can
Fig 2. Separable Reversible Data Hiding [1]
be separately recovered as this method is separable unlike
basic reversible data hiding. Also it is more efficient, more
flexible and secure than reversible data hiding. Disadvantage
is that, this method though efficient than reversible data
hiding, it do not consider about the security of the secret key
used in the encryption and embedding of data.
C. Separable Reversible data hiding using AES Algorithm
In this method, first the data is taken and is encrypted using
AES algorithm [2]. The image system would auto generate the
keys for encrypting the data as well as the image. The least
significant bits (LSB) of the encrypted image is compressed to
provide space for embedding the data. This is done using
Lossy compression technique.
Fig. 3. Separable reversible data hiding using AES algorithm[2]
At the receivers end, the encrypted image, containing the
encrypted data is obtained and is processed. If the receiver has
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both the data encryption key as well as the data embedding
key, he can successfully extract the data but cannot get the
image (Fig 3).
If the receiver has the data embedding and the image
encryption key, he can retrieve an image similar to the original
one with accuracy of about 80 percent, but cannot get the
additional data [2]. If the receiver has all the three keys, i.e.
the image encryption key, the data encryption key as well as
the data embedding key, the receiver would be able to extract
the original data, additional data, and also recover the original
image similar to the original one. The various phases of this
technique are: Registration, Image encryption, Data
encryption, Data embedding, File sending, Image decryption,
Data extraction and decryption.
III. PROPOSED SYSTEM
As data hiding is an important activity in most of the
highly secure applications like military, remote sensing data
analysis and so on, it is important to identify a highly secure
method. The method must be simple in its architecture and the
algorithms used must be efficient and must satisfy the
requirements of such sensitive applications.
The proposed system is an integration of some of the basic
methods which were discussed in the previous section. For
simplicity, efficiency and flexibility, the Separable reversible
method can be used along with some aditional features.
The proposed system consists of the following phases:
A. Login
The actors of the system must register for every first time
they use the system. After that the can login using a login id
and a unique password. Every user must login into the system
before carrying out any activities. This is to ensure
authentication of genuine users of the system. User
authentication is the first measure taken for security.
To filter out mechanised login attacks, Captcha feature is
enabled. This is to ensure that the actor is a human and not a
robot or any other devices. This forms the next layer of
security.
Fig. 4. Block diagram of Proposed system
B. Image Encryption
In this phase the actor has to select a particular image as the
cover media for embedding the secret message into it. The
image may be one relevant to the message being transmitted
or may be an unwanted irrelevant image used just for the sake
of transmission.
The actor is provided with two algorithms, DES and AES.
Depending upon the application they may be chosen.
Application wich requires less security and complexity can opt
for DES, and one which require very high security for its
highly confidential data but can compromise on the
complexity of the system, can opt for AES algorithm. This
forms the next higher level of security based on the
confidentiality of the data being transmitted. For both the
cases an encryption key is necessary. The key required will be
automatically generated and the method used is explained in
phase D.
C. Data Encryption and Embedding
After encrypting the image, the next step is to encrypt the data
i.e. the secret message and then embedd it into the encrypted
image. Here also alternatives are provided by the interface to
choose among the encryption standards i.e. DES and AES.
After encryption, the data will be embedde into the previously
encrypted image using the LSB embedding technique. The key
required for encryption of data is also generated automatically
ny the system.
Hence a complex form of encrypted image with encrypted
data embedded on it has been obtained. This complex is then
send to the destination or the authorised receiver.
D. Key generation and Exchange
Key generation phase runs in the background of the other
phases explained above. In this phase, a Random key
generation technique is used and along with that, a Key
Fig. 5. Diffie-Hellman Key Exchange block diagram
exchange system has been integrated to make the system more
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efficient and resistent to malicious attacks. Thus this phase
provides one among the multiple layers of security. The secure
key exchange method adopted is Diffie-Hellman Key
exchange method which is one of the simplest as well as
efficient method used for secure key exchange. Security is
also provided to ensure that the data is received at the right
hands. For this, the sender is provided with an alternative to
select the respective receiver of the message that he desire to
send. Only the selected actor or person would be able to
retrieve the data at the destination. Any other actor, even with
the respective keys would not be able to decrypt the data. The
authentication module was introduced to cover the drawback
of Diffie Hellman Key Exchange. Diffie Hellman Key
excahnge do not provide povisions to authenticate the actors
or to ensure that the data has been received by the right
person.
F. Data Extraction
At the receiver side, after the complex data has been obtained
in the right hands, the next step is to extract all the relevant
data from this complex. For this the receiver must have all the
keys i.e. the encryption keys as well as the data embedding
keys. In this phase, the receiver can extract data if he is an
authenticated user of the system, heis having the Data
extraction keys and also he is the mentioned receiver by t he
source. The data would be allowed to extract only if he is the
desired receiver of the data. If any other authorised user try to
access the data using the relevant keys, he would be denied
from doing this process.
The data can be extracted using reverse algorithms. For
extracting the encrypted data from the image, the reverse LSB
method is used. After that the encrypted data is extracted. If
the data was encrypted using DES algorithm, at the receiver
side, the system would be using reverse DES. Similar is the
case of AES algorithm. The extraction of the data can be done
either before or after decrypting the image. This is because the
basic system used is separable unlike Reversible Data Hiding.
G. Image Recovery
This phase can be executed before or after the data extraction.
The algorithms used is the respective reverse methods of one
used in the encryption process i.e. reverse DES or reverse
AES depending upon the one chosen by the encryptor.
This is the overview of how the system works and the
individual phases, in case of data transmission from source to
destination.
IV. EXPERIMENTAL RESULTS
Tests were carried out to check the efficacy of the system. The
results showed that the existing systems were less secure than
the proposed one in terms of the keys that they use for data
security. Also the proposed system has methods to prevent
some of the attacks which was absent in the previous system.
The system also provides user authentication system making
the new system a formidable method for data security. The
proposed system also provide flexibility of chosing algo-
rithms with different strengths, making the system application
friendly. AES algorithm used for encryption of data as well as
image is secure but complex in its architecture. So it can be
used as a tradeoff between complexity and efficiency of the
system.
The PSNR value of four sample images were calculated by
comparing their original image with their respective recreated
image. The values obtained were in the range of 30 to 50. This
implies that the recreated images are of acceptable quality.
Thus the system helps in recreating good quality image
effectively in terms of PSNR and hence it is an acceptable
method in the field of data security.
Table 1. . List of PSNR value of Sample Images
The above results shows that the novel method can be used
as an acceptable alternative for other basic data security
systems in terms of efficiency, flexibility and security.
V. CONCLUSION
Importance of securing data has lead to the development of
many models and systems. Using a method like Separable
reversible data hiding would make the security process more
efficient and would satisfy all the basic requirements of a data
securing system. Integrating this system along with a key
exchange technique like Diffe- Hellamn to secure the keys
used for encryption and embedding, would fix the system’s
flaws. Adding different security measures would provide with
an effective alternative in the field of data science.
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